PREVIOUS WORK: Regional prevalence and familial aggregation of essential hypertension influenced us to seek predictors of the disorder in normotensive progeny of hypertensive parents (cases) and matched children of normotensive parents (controls). Physiological (heart rate, ECG, blood pressure, and heart function by echocardiography) and biochemical measurements (plasma norepinephrine and renin activity (PRA), and urine prostaglandin E-like substance and kallikrein) were made before, during and after the stress of exercise in black and in white chidren, aged 10-17 years. Significant differences between cases and controls occurred only in the blacks. Cases had higher supine systolic and maximum diastolic blood pressures; lower post-exercise kallikrein and lower PRA's. Black children (cases and controls) had higher resting and exercise blood pressures; higher sodium excretion; lower PRA's and lower potassium excretion than white children. Black cases showed lower kallikrein activity in post-exercise urines than white cases. Sex differences were seen in blood pressure, sodium/potassium and kallikrein excretion and PRA. Two-year followup examinations are underway. HYPOTHESES: That physiologic and biochemical variables associated with hypertensive disorders can be detected in careful evaluations of appropriate groups of young people and may reflect early vasoregulatory abnormalities. LONGITUDINAL STUDY: The proposed research is to repeat biannual, outpatient examinations of the previously described black or white adolescents for another 4-year period. Physiological and biochemical measurements will be made during rest and stress exercise as before. Serum aldosterone levels and new measurements for urinary kallikrein and 6-keto prostaglandin F1 alpha will also be made.